A. Field of the Invention
This invention relates to a modified Fletcher-Suit after-loading cervical applicator for use in brachytherapy. The invention includes a tandem and colpastat tube arrangement permitting introduction of radio-emissive material to intracervical tissues where the tubes are combined with at least one balloon that is inflatable in situ with a radiation attenuating fluid to positionally stabilize the applicator in the patient and provide selective shielding during high dose rate brachytherapy.
B. Description of the Art
Since shortly after the Curies"" discovered radioactivity, radiotherapy has been used in connection with treatment of proliferative tissues and, particularly, in connection with cancer treatments and other oncological procedures. The two major categories of radiotherapy are teletherapy and brachytherapy. Teletherapy utilizes an external radiation source generally directed to a select region of the body to destroy cancer cells. Brachytherapy involves directly implanting/embedding a radioactive source within or proximate to a target cancerous mass for localized exposure.
Numerous medical devices and adjuncts have been developed for cervical cancer brachytherapy. An important early development was the Fletcher-Suit cervical applicator. The Fletcher (standard shielded) applicator provided a technique for intracervical/intrauterine introduction of a radioactive source. The traditional Fletcher applicator is employed in low dose therapies and comprises three hollow, metal tubes. The two, flanking xe2x80x9ccolpastatxe2x80x9d tubes provide for intravaginal positioning and the medially disposed intrauterine xe2x80x9ctandemxe2x80x9d tube is adapted to traverse the vaginal canal and project into the cervix. The conventional Fletcher-Suit system design suffers from a known in situ positioning problem attributed, in part, to the absence of a secure connection between the colpastat tubes and the tandem tube.
Variations of the Fletcher-Suit applicator for intrauterine brachytherapy have evolved from its original form. For example, in Weeks U.S. Pat. No. 5,562,594 a modified Fletcher tandem device providing shielding for protection of untargeted tissues is described. The Weeks applicator features an inflatable lumen applicator with one embodiment incorporating dual inflatable balloons for delivery and placement of radioactive fluid for temporary brachytherapy. The stated purpose of the Weeks applicator is to reduce the dose of radiation applied to internal organs, such as the rectum, without the need to decrease the dose targeted at the tumor-bearing areas. Because Weeks contains a relatively comprehensive discussion of the physics and anatomy associated with intracervical brachytherapy using a Fletcher tandem, its content is incorporated herein by reference.
Schoppel et al., in U.S. Pat. No. 5,012,357, discloses an intracavity brachytherapy applicator permitting xe2x80x9cafter-loadingxe2x80x9d shielding particularly useful in CT scanning procedures. Morrison, in U.S. Pat. Nos. 4,244,357 and 5,947,891, discloses a dual tube brachytherapy delivery system including at least one hollow tube (an intravaginal tube) having an inner end adapted for insertion into the vaginal cavity, and a second hollow tube (an intracervical tube) having an inner end adapted for insertion into the cervix and the uterus. Finally, by way of exemplary prior art technologies, Weinberger, in U.S. Pat. No. 5,924,973, describes an applicator incorporating a balloon catheter in fluid communication with an indiflator for inflation with a radioactive fluid.
Brachytherapy is divided into two major classifications, low dose rate (LDR) and high dose rate (HDR). Low dose rate treatments typically involve dose rates of 40 to 60 centigray per hour and more typically about 55 centigray/hr. High dose brachytherapy, on the other hand, contemplates significantly higher rates of dose delivery (up to 1000 centigray per minute) and not uncommonly in the range of hundreds of centigray in minutes. High dose and low dose brachytherapy are generally believed to be of substantially equal efficacy oncologically, albeit that HDR is generally recognized to provide significant delivery efficiencies over a low dose alternative. Notwithstanding significantly enhanced radiation delivery efficiencies, many hospitals and medical treatment providers have opted not to use HDR treatments due to reportedly higher incidences of complications of which the most frequent complications arise from radiation damage to healthy tissues and organs proximate to the implanted/embedded radiation source. The risk of such complications resulting from HDR treatment is believed to have steered some healthcare professionals to conventional LDR techniques and/or use of hybrid LDR/HDR delivery schemes providing radiation delivery at a substantially augmented rate relative to LDR but at a substantially reduced rate from HDR. Thus, while reportedly reducing the risk of complications, such hybrid treatments also represent a corresponding loss of delivery efficiencies.
In brachytherapy associated with treatment of cervical cancer, LDR treatment minimizes collateral and undesirable damage to healthy tissues, e.g. the bladder and rectum, but achieves its therapeutic effect only by subjecting a patient to prolonged periods of immobilization during exposure. Thus, it is not unusual for LDR procedures, particularly in the treatment of cervical cancer, to require hospitalization for days. Furthermore, prolonged procedures result in patient aggravation, inconvenience, and discomfort while also significantly increasing treatment costs attributable to extended hospitalization, all without any significant augmentation in efficacy.
In contradistinction, HDR intra-cervical brachytherapy provides an efficient alternate therapeutic option. HDR may significantly reduce, from days to minutes, the duration of exposure and patient immobilization. Thus, HDR eliminates the need for prolonged hospitalization and reduces patient inconvenience and discomfort without a loss of therapeutic efficacy. In short, reliance on HDR provides significant advantages in healthcare delivery efficiency, minimizes patient discomfort, and even permits outpatient treatment.
Recognizing both the value and potential harm from HDR, healthcare providers have turned to various shielding techniques to minimize undesirable collateral tissue damage in HDR brachytherapy procedures. However, such shielding is difficult to use and difficult to position in situ. Even minor displacement of selective radiation attenuating shielding in situ defeats the benefit provided thereby. If displaced, the shielding not only fails to diminish exposure of healthy tissues but also may obstruct exposure of targeted proliferative tissues. Moreover, the use of effective shielding is increasingly difficult where the applicator embodies complicated structures that either interfere with or are interfered with by the shielding.
Conventional shielding material, e.g., metal, barium fluids, etc. are opaque to radiation which serves admirably to attenuate impinging radiation. However, the very radiation attenuating excellence also obstructs efficient monitoring of the general area by electromagnetic-based instrumentation, for example, tomographs, magnetic resonance imagers, etc. and the more traditional x-rays and fluoroscopes. Finally, conventional shielding does not contribute to stable positioning of the applicator during treatment in conjunction with its function to shield healthy tissue from exposure.
It is, therefore, an object of the present invention to address and overcome problems of the prior art brachytherapy apparatus and methods.
It is another object of this invention to provide a highly efficient and efficacious intracervical and intervaginal brachytherapy delivery system.
Another object of this invention is to provide selective attenuation of radiation emitted from an internally disposed radiation source without reducing dose rate exposure to a selected target.
A further object of the invention provides an applicator for intra-cervical HDR brachytherapy that attenuates radiation exposure of proximate healthy, non-target tissue.
It is still another object of the invention to improve intra-cervical brachytherapy delivery while minimizing patient discomfort and inconvenience.
Still another object of the invention is to maintain therapeutic efficacy and maximize delivery efficiencies of intra-cervical and transvaginal brachytherapy.
A more particular object of this invention is to provide unattenuated delivery of high dose rate radiation to a proliferative tissue/tumor zone by intra-cervical/transvaginal brachytherapy while providing a radiation-attenuating prophylactic for proximate tissues such as the bladder and rectum during intra-cervical HDR brachytherapy.
A final stated, but only one of additional numerous objects of the invention, is to provide a radiation attenuating apparatus and method that is at once effective, inexpensive and easily deployed in for HDR brachytherapy procedures.
These and other objects are satisfied by a modified Fletcher-Suit applicator for delivery of an irradiation source used in brachytherapy comprising:
an elongated, rigid tandem tube having a proximal end including an opening and a closed distal end where the tandem tube has a sufficient length to project transvaginally and a select distance into the cervix, said tandem tube defining a hollow bore and permits selectively removable insertion of a radioactive source from said proximal opening to the distal end;
a colpastat tube;
rigid connecting means for affixedly connecting the tandem and colpastat tubes at a select distance therebetween;
inflatable balloon means mounted on a select one of said tubes for positionally securing said applicator within a patient""s vaginal canal, to positionally secure the applicator intravaginally, and for providing attenuation of radioactive emissions from the radioactive source to tissues proximate to the balloon; and
fluid communication means for communicating radiation-attenuating fluid between a reservoir and said balloon and cause the inflation and deflation thereof.
The foregoing and other objects are satisfied by a brachytherapy method comprising:
inserting an applicator transvaginally where the applicator includes a rigid tube of a length sufficient to project intracervically and the tube has affixed thereto an inflatable balloon where the balloon is positionable within the vaginal canal;
inflating the balloon with a radiation attenuating fluid where the balloon expands against the wall of the vaginal canal to to positionally secure the applicator intravaginally;
urging the vaginal canal wall away from the tube, and
inserting a radioactive sample into the applicator.
In short, the present invention provides a cervical applicator for brachytherapy which is capable of attenuating the dose of radiation exposure of selected tissues in the proximity of the target tissue and also contemplates a method of employing a cervical applicator for brachytherapy, to securing the applicator intravaginally, and a method for attenuating radiation exposure to untargeted tissues during brachytherapy.
According to one aspect of the present invention, a cervical applicator for use in intracervical brachytherapy includes a tube assembly for insertion through the vaginal canal and into the cervix. The tube assembly comprises a transvaginal portion connected to an intracervical tube portion with at least one inflatable balloon mounted proximally to the distal end of the intracervical portion of one of the tubes. Following introduction and preliminary positioning through the external os of the intracervical tube portion, the balloon is inflated with a radiation attenuating fluid from an external reservoir in fluid communication with the balloon. As the balloon inflates, it expands and upon reaching a sufficient inflation pressure, presses against and displaces the vaginal wall from the tubes.
As in the case of a typical Fletcher-Suit applicator, the invention uses the balloon arrangement to provide intravaginal positional stabilization and displacement of vaginal tissues. The particular balloon arrangement, however, may vary. For example, the balloon may itself comprise an annular member physically attached to and surrounding the transvaginal/intracervical tube of the applicator. Alternatively, the balloon may be mounted on a supporting platform mounted on the tube or may be attached or affixed to the applicator tube without surrounding the tube.
In general terms, the invention herein contemplates a brachytherapy method and adjunct calling for the transvaginal insertion of a cervical applicator providing a projecting tube portion for intra-cervical disposition and a combination radiation attenuating, tube-position-stabilizing balloon for in situ inflation. Upon inflation, the selected position of the applicator is thereby fixed relative to the vaginal canal and uterine cavity by, at minimum, an interference fit with the vaginal wall and cervix, and more desirably, by pressing with sufficient force on the vaginal wall to induce displacement thereof from the tube and to provide selected radiation attenuating shielding of nearby healthy tissues. Once the health care provider is satisfied with the physical disposition of the device and shielding the radiation source may be introduced in the conventional manner through the tube passage and to the proximal tip of the tube which, ideally has been positioned at or near the target tissue/mass. As a consequence, the balloon protects internal tissues/organs adjoining the vagina by increasing the distance thereof the radioactive source as well as providing attenuating shielding to significantly decreasing radiation exposure during HDR of the organ/tissue.
The foregoing and other objects and advantages will appear from the description to follow. In short, the invention herein is directed an original or retrofitted intracervical applicator for HDR brachytherapy providing maximum radiation delivery efficiencies to targeted tissues while mitigating adverse effects to such exposure of proximate healthy tissues. The invention contemplates both apparatus dedicated to its employ and converting existing structures using off-the-shelf basic components already available to healthcare delivery professionals.
For definitional purposes and as applicable, the inner tube end is referred to as xe2x80x9cdistalxe2x80x9d and the end accessible for manipulation by the healthcare provider is referred to as xe2x80x9cproximalxe2x80x9d (typically projecting external of the patient""s body).
As used herein xe2x80x9cconnectedxe2x80x9d includes physical, whether direct or indirect, permanently affixed or adjustably mounted, as for example, the balloon on the transvaginal tube portion of the apparatus or the case of two tubes in a tandem. Thus, unless specified, xe2x80x9cconnectedxe2x80x9d is intended to embrace any operationally functional connection.
As used herein xe2x80x9csubstantially,xe2x80x9d xe2x80x9cgenerally,xe2x80x9d and other words of degree are relative modifiers intended to indicate permissible variation from the characteristic so modified. It is not intended to be limited to the absolute value or characteristic which it modifies but rather possessing more of the physical or functional characteristic than its opposite, and preferably, approaching or approximating such a physical or functional characteristic.
In the following description, reference is made to the accompanying drawing, and which is shown by way of illustration to the specific embodiments in which the invention may be practiced. The following illustrated embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that other embodiments may be utilized and that structural changes based on presently known structural and/or functional equivalents may be made without departing from the scope of the invention.
Given the following detailed description, it should become apparent to the person having ordinary skill in the art that the invention herein provides a brachytherapy adjunct and method designed for use in HDR procedures thereby permitting exploitation of the significantly augmented delivery efficiencies provided by HDR while mitigating the complications arising from its use.